Lycopene is a carotenoid that is found in red fruits, such as tomatoes and watermelons. Carotenoids are natural pigments that act as antioxidants for the body. Antioxidants serve to lessen the effects of free radicals, which are attributed to be responsible in damaging the cells in the body.
Lycopene, a polyene hydrocarbon, an acyclic open chain unsaturated carotenoid having 13(C—C) double bonds, of which 11 are conjugated double bonds arranged in a linear array. Two central —CH3 groups are in the 1, 6 position, while the remaining —CH3 are in 1, 5 position relative to each other. Color and antioxidant properties of lycopene are due to an extended system of conjugated double bonds.

Lycopene gets its name from the species classification of tomato, Lycopersicon esculentum. It is the principal hydrocarbon carotenoid in tomatoes with lesser amounts of other carotenoids. The composition of carotenoids in tomato fruits are: lycopene (C40H56), 80-90%; α-carotene (C40H56), 0.03%; β-carotene (C40H56), 3-5%; γ-carotene (C40H56), 1-2%, phytoene, (C40H64), 5.6-10%; phytofluene (C40H64), 2.5-3%; neurosprene (C40H64), 7-9% and lutein (C40H58), 0.011-1.1% (Gross. J, 1987, Pigments in Fruits, Academic Press, London)
The antioxidant activity of lycopene is due to its ability to trap peroxy radicals. It exists in a variety of geometric isomers such as: all-trans, mono-cis, and poly-cis forms. In nature, lycopene exists in all-trans form and seven of these bonds can isomerise from the trans-form to mono or poly-cis form under the influence of heat, light or certain chemical reactions. The all-trans-isomer is the most predominant isomer in fresh tomatoes and is the most thermodynamically stable form. Lycopene undergoes trans- to cis-isomerisation during processing and storage. In various tomato based foods, trans-isomer is 35-96%, 5-cis-isomer is 4-27%, 9-cis- and 15-cis isomer with considerably lower amounts.
Cis-isomers of lycopene have physical and chemical properties distinctly different from their all-trans counterparts. Some of the differences observed in cis-isomers are decreased colour intensity, lower melting points, smaller extinction coefficients, and a blue shift in the ultraviolet spectrum known as cis-peaks which help in identification. The cis-isomers are more polar, more soluble in oil and hydrocarbon solvents and less prone to crystallization due to structural configurations.
During tomato processing, lycopene may also undergo degradation due to exposure to heating in the presence of metallic ions such as cupric, ferric, etc. and oxygen. During the product storage, the conversion of lycopene cis-isomer to trans-isomer can occur because cis-isomers are unstable whereas trans-isomers are stable in the ground state. Cis-isomers of lycopene are also known to be more soluble in bile acid micelles and may be preferentially incorporated into chylomicrons when compared to trans-lycopene. (Boileau et al., J. Nutrition. 129, 1176-1181(1999).
It is likely that there is an in-vivo isomerisation of trans- to cis-lycopene within the body. Another possibility is cis-isomers are more bio-available than trans-form as reported in the case of consumption of heat processed tomato products containing higher amounts of cis-lycopene compared to fresh tomato products having largely trans-lycopene [Shi and Maguer, Crit. Rev. Biotechnol. 20, 293-334 (2000)]. Tomato pulp powder and tomato pulp waste obtained from heat processed tomato at 82 degree C. and removing the juice showing cis-lycopene constituting around 56.8% of total lycopene and it may be a potential source for preparing cis-lycopene enriched tomato oleoresin [Wang and Chen. Eu. Fd. Res. Technol-222, 347-355 (2006)]. There is evidence that cis-lycopene is more bio-available than trans-lycopene (Un Lu et al., Brit. J. Nutr. 98, 140-146, 2007).
Supercritical carbon dioxide extraction of lycopene in tomato skins showed good recovery of total lycopene and ethanol and acetone were used as modifiers. The stability of lycopene stored in solvent was improved through the addition of alpha-tocopherol or rosemary extract [Ollanketo et al., Eu. Fd. Res. Technol, 212, 561-565(2001)].
A procedure is described for the supercritical fluid extraction of all-trans lycopene from dried and powdered tomato skins using carbon dioxide, density 0.9 g/ml, resulting in 88% all-trans-lycopene in the extract [Salud Gomez-Prieto et al., J. Agr. Fd. Chem. 51, 3-7 (2003)]. The study showed that the extraction pressure and the SCF carbon dioxide density are the determining factors assisting in preferential solubility of cis or trans-isomer of lycopene.
In human plasma, lycopene is an isomeric mixture, consisting of at least 60% of the total lycopene as cis-isomers [Yang Kun et al., Lycopene: its properties and relationships to human health; Fd. Rev. International. 22, 309-333 (2006)]. The isomers such as all-trans-; 5-cis-; 9-cis- and 13-cis-lycopene were identified in plasma with configurational stability sequence being 5-cis→all-trans→9-cis→13-cis→15-cis-lycopene.
However, in the computational model study 5-cis-lycopene had the highest antioxidant property as indicated by the ionization potential, the sequence being 5-cis→9-cis→7-cis→13-cis→15-cis→all-trans-lycopene [Chasse et al., J. Mol. struc. (Theochem) 571, 27-37 (2001); cited in Adv. Fd. and Nutr. Res. 51, 99-164 (2006), Rao et al.]
Most stability studies on lycopene in food system concerns degradation. Lycopene may be partially destroyed in processed tomato products by heating in the presence of metallic ions or oxygen. Lycopene may be expected to undergo at least two changes during tomato processing, isomerisation and oxidation. Lycopene isomerisation can take place during processing. On the other hand, the conversion of cis-form to trans-form can occur during storage [John Shi et al., Lycopene in tomatoes: Chemical and physical properties affected by food processing, Critical reviews in food science and nutrition, 40, 1-42, (2000)].
Lycopene acts as a preventive agent for cancer. Lycopene is important, because it appears to provide protection against prostate cancer, lung cancer and a broad range of epithelial cancers [Micozzi et al., Carotenoid analysis of selected raw and cooked foods associated with lower risk of cancer, Journal of Natl. Cancer Institute, 82, 282-28 (1990)]. The intake of lycopene has been found to be associated with reduced risk of cancers of other sites such as digestive tract, pancreas and bladders. It was found that women with higher levels of blood lycopene had consumed higher levels of lycopene and vitamin A and had one third less chance of developing cancer.
Lycopene consumption obtained from fruits and vegetables may reduce likelihood of developing heart disease. It prevents oxidation of low density lipoproteins, cholesterol and reduces the risk of developing atherosclerosis and coronary heart disease. [Kristenson et al., Antioxidant state and mortality from coronary heart deceases in Lithuanian and Swedish men: Concomitant cross sectional study of men aged 50, Brit. Med. J. 314, 629-633 (1997); Kohlmeir et al., Lycopene and Myocardial Infarction risk in the EURAMIC study, American Journal of Epidemiology, 146, 618-626 (1997)]
Bio-availability is defined as the fraction of an ingested nutrient that is available to the body through absorption for utilization in normal physiological functions and for metabolic process.
The composition and structure of food have an impact on bio-availability of lycopene, which may affect the release of lycopene from the tomato tissue matrix. Cooking or fine grinding of foods could increase the bio-availability by disrupting or softening plant cell walls and disrupting lycopene-protein complexes. Thermal processing such as cooking and mechanical texture disruption such as chopping are convenient ways to enhance bio-availability by breaking down study cell wall structures, disrupting chromoplast membranes, and reducing cellular integrity thus making lycopene more accessible. It was found that 20-30% of total lycopene consisted of cis-isomers when tomatoes were heated to 100° C. for 1 hour. [Stahl et al., Uptake of lycopene and its geometrical isomers is greater from heat processed than from unprocessed tomato juice in humans, J. Nutrition, 122, 2162-2166 (1992)].
Lycopene bio-availability from tomato based food is significantly higher than from fresh tomatoes; co-ingested with oil. Thermal treatment and oil medium are required to extract lycopene into the lipophobic phase. It was assumed that heating tomato juice in the presence of corn oil for 1 hour converts lycopene from the trans- to cis-form, thereby increasing the level absorption by the human body.
Various dietary fibres reduce the bio-availability. Pectin, a typical dietary fibre affected the absorption of dietary carotenoid in humans. High-methoxy pectin is associated with the hypocholesterolemic effect of dietary fibres and low absorption promoting high viscosity condition.
Absorption of lycopene seemed to be more efficient at lower dosage and lycopene ingested with β-carotene was absorbed more than when ingested alone. A strong decrease in serum lycopene levels were seen after high dose β-carotene supplementation. [Jackson, M. J., The assessment of bio-availability of micro-nutrients; Introduction, European Journal of Clinical Nutrition, 51, S1-S2 (1997)]
Food processing may improve the availability of lycopene. The lycopene bio-availability from tomato based food may be enhanced in two ways; extraction of lycopene from the food matrix into the lipophilic phase and thermal process and mechanical disruption of tomato tissue cells. Lycopene in a lipid medium is more bio-available than in fresh tomatoes. Extensive cooking could also destroy lycopene. Optimum processing technology parameters should be found to maximize destruction of the matrix and minimize the destruction of lycopene [Gartner et al., Lycopene is more bio-available from tomato paste than from fresh tomatoes, Amer. Journal of Clinical Nutrition 56, 116-122 (1997); Brown et al., Plasma carotenoids in normal men after a single ingestion of vegetable or purified beta-carotene, Journal of clinical Nutrition 49, 1258-1265 (1989)].
Lycopene is lipo-soluble; it is usually extracted with a solvent such as chloroform, hexane, acetone, benzene, petroleum ether or carbon disulphide, however a safe solvent is preferred. In cases where a solvent extraction may be slow and incomplete, efficient mechanical grinding of the material is used to facilitate the complete extraction. Dehydrated material may be extracted with water immiscible solvents. Moistening of the dehydrated material prior to solvent extraction is necessary to get complete extraction. Because of sensitivity, extraction is done in dim light and inert atmosphere. To avoid oxidation and isomerisation during extraction, anti-oxidant such as quinol and neutralizing agent such as calcium hydroxide may be added. Extracted sample should be stored in dark under nitrogen in the freezer (−20° C.).
After extraction, saponification is the most effective method of removing unwanted lipids, chlorophylls and other impurities. Further purification and crystallization of the product can be obtained by fractional crystallization from petroleum ether or acetone at low temperature. Some rapid and efficient method for lycopene analysis and identification have been developed using microwave-solvent extraction, pressurized accelerated solvent extraction technologies in which lycopene recoveries from tomatoes ranged from 98.0-99.6%. [Sadler et al., Rapid extraction of beta-carotene and lycopene from reconstituted tomato paste and pink grape fruit homogenates, Journal of Food Science, 55, 1460-146 (1990); Benthin et al., Pressurized liquid extraction of medicinal plants, J. Chrom., A. 831, 211-219 (1999)]
The determination of lycopene content in tomato and tomato based foods can be carried out by physical and chemical methods. Physical methods are based on the relation of colour parameters with lycopene concentration of the samples. In chemical analysis lycopene is extracted from the tomato tissues and quantified.
Colour measurement has been a convenient and less tedious method for assessing the quality than the chemical analysis method. The deterioration in a quality may be due to the loss of natural pigment. The measurement of chromaticity values with a colorimeter would be useful if it could accurately estimate lycopene concentration in tomato samples after harvest and processing. It will not predict lycopene concentration accurately enough to substitute for chemical extraction analysis.
Spectrophotometric methods: Hexane and acetone are used for extraction of lycopene from tomato tissues and the absorbance is measured at 460-470 nm. A pure sample is necessary for calibration curves.
HPLC method: Reverse phase HPLC method using C18 stationary phase allows for the partial separation of cis- and trans-isomers of pro-vitamin A carotenoids. Mobile phase: Acetonitrile/THF 85/15 diluents IPA/THF 80/20+0.5% BHT. Flow rate 1.5 ml/minute. Run time for 20 minutes.
For processing, tomatoes are washed, sorted and sliced. Sliced tomatoes undergo a hot or cold break method for juice preparation. Juice from tomatoes is usually obtained using screw or paddle extractors. In the manufacturing of other tomato products such as pulp, puree, paste and ketchup, tomato juice is concentrated with steam coils or vacuum evaporators. For canned tomatoes, sliced or whole tomatoes are retorted. For dried, tomato undergoes dehydration methods. Degradation and colour loss may precede and tomato products are affected by a number of factors. The main cause of lycopene degradation is isomerisation and oxidation.
In tomato, the outer pericarp has the highest lycopene and other carotenoids content and the outer wall and the lobular contents have the highest carotene. Tomato skin contains 12 mg lycopene/100 g, while mature tomato contains 3.4 mg lycopene/100 g. The concentration of lycopene in tomato skin is about 3 times higher than in mature tomatoes. Skin and the pericarp of tomato fruits are rich in lycopene. Most of the lycopene is found attached to the insoluble fibre portion of the tomatoes.
Chemical and physical properties of lycopene: melting point—172-175° C.; solubility-soluble in chloroform, hexane, benzene, carbon disulphide, acetone, petroleum ether; sensitivity-light, oxygen, high temperature, acids, metallic ions such as Cu (II), Fe (III) catalyse its oxidation. λ max (trans)-lycopene, 446 nm (E1%-2250), 472 nm (E1%-3450), 505 nm (E1%-3150)
The deterioration in colour occurs during the processing of various tomato products resulting from exposure to air at high temperature during processing causing naturally occurring all trans-lycopene to be isomerised and oxidized. Coupled with exposure to oxygen and light, heat treatments that disintegrate tomato tissues can result in the destruction of lycopene. These changes are mainly due to heat stress imposed by the relatively harsh thermal process required for the shelf life stability of the processed tomato products.
Temperature affects the nature and extent of lycopene breakdown. Oxidative degradation of lycopene at 50 degrees C. leads to fragmentation of molecules giving acetone, methyl heptanone, levulinic aldehyde and probably glyoxal as products. Loss of lycopene can occur when the holding time at high temperature is long. Length of heating is a critical factor in controlling the degradation of lycopene. It appears that de-aeration and high temperature-short duration heat treatment can have beneficial effects on the retention of colour quality.
The most important contributing factor for the oxidative destruction of lycopene is the availability of oxygen. More than 30% of lycopene is degraded when heated at 100 degree. C in the presence of oxygen, while 5% was lost in the presence of carbon dioxide. [Cole et al., Stability of lycopene. I. Degradation by oxygen, J. of Science food Agric, 8, 360-365 (1957)]. The magnitude of lycopene destruction by exposure to increased lighting is less compared to the increased temperature.
The dehydration of tomato slices is carried out at high temperature over an extended period under vacuum. The general tendency of lycopene retention in samples decreases slightly during dehydration. During osmotic dehydration, lycopene content remains constant. The explanation is that the sugar solution in osmotic dehydration keeps oxygen away from tomatoes and reduces oxidation of lycopene at low operating temperatures. Heat treatment disintegrates tomato tissues and increased exposure to oxygen and light, which resulted in the destruction of lycopene.
Total Lycopene and cis-isomer content in the dehydrated tomato samples [Shi, et al., Lycopene degradation and isomerisation in tomato dehydration, Food Res. Intl. 32, 15-31 (1999)]
LycopeneCis-Total lycopenelossAll-transIsomerSample(mcg/g dry basis)(%)(%)(%)Fresh tomato77501000Osmotic treatment77501000Osmo-Vac dried7372.493.56.50Vac-dried7313.289.910.10Air-dried7263.9084.416.6
Peeling is an important operation in tomato processing. Chemical treatment includes lye peeling in a hot solution of sodium hydroxide or calcium chloride.
Physical treatment includes steam peeling by high pressure or superheated steam. New peeling methods such as cryogenic scalding with liquid nitrogen, liquid air or Freon-12 or IR peeling with infrared radiation as heat source. During lye peeling, the hot solution dissolves the epicuticular waxes, penetrates the epidermis, digests the middle lamella, cell walls and causes separation of skin. The concentration of lye solution and temperature used range from 8-25 degree C. and from 60-100 degree C. depending on the cultivar and fruit maturity. With steam peeling, tomatoes are exposed to live steam long enough to loosen the peel but not so long as to cause flush softening or cooking Both chemical and steam peeling cause relatively high losses of edible parts of the outer pericarp layer of tomato fruits. Schulte (1965) found that peeling tomatoes with the infrared method produce a peel loss of 5.30% while steam method had a peel loss of 7.50% (W. A. Schulte, Efficiency of chemical and physical tomato peeling systems and their effects on canned products quality, Ph.D. Thesis, p. 199, 1965, Ohio State Univ. USA) The wastes during tomato processing are mainly seeds, pericarp tissues and skin residues. The epidermal area of tomatoes contains more than 80-90% of total lycopene in tomatoes. It is clear that large quantity of lycopene is normally discarded as tomato processing waste. This waste is an important source of lycopene in the food industry.
Reduction of lycopene content and trans-cis-isomerisation results in reduction biological property.
Total lycopeneSamplemg/100 gAll-trans, %5-cis, %9-cis, %13-cis, %other Cis-%Tomato paste52964<1<1<1(Italy)Tomato paste3.791512<1(Germany)Tomato Ketchup9.5887231(Italy)Tomato Ketchup3.0768565(USA)Instant meal0.6768565(Swiss)Sauce (Italy)3.0935<13<1Canned tomatoes7.10845353(Schierle et al., Content and isomeric ratio of lycopene in food and human blood plasma. Food chem. 59(3), 459-465 (1996)
Bioactivity potency depends on the extent of the isomerisation and oxidation as well as the stability when the tomato-based products are subjected to processing during storage. Heat, light, acids and other factors have been reported to cause isomerisation. A true assessment of the quality and health benefits of processed tomato based foods depends not only on the lycopene content but also on the distribution of isomers. Controlling lycopene isomerisation behaviour during production and storage of tomato products can benefit in improved product colour and quality.
Thermal processing: Heat treatment clearly increases the percentage of cis-isomer. Heating tomato-based foods in oil had a bigger effect on isomerisation than heating in water. Not only duration and temperature of heat treatment but also the food matrix components such as oil or fat influence the lycopene isomerisation.
Effects of dehydration: Dehydration method shows a significant increase in cis-isomer and simultaneous decrease in all-trans isomers. In osmotic treatment predominant mechanism is isomerisation while air-drying isomerisation and oxidation are the two factors affecting the total lycopene content and biological potency. Dehydration and increase of surface area generally leads to poor stability. Osmotic solution (with sugar) remaining on the surface layer of tomato prevents oxygen from penetrating and oxidizing lycopene. Therefore, osmotic treatment could reduce lycopene losses compared with other dehydration methods.
Lycopene degradation and colour change: Colour retention in tomato is better at lower temperature. The colour quality remains unchanged during osmotic treatment.
Lycopene stability during storage: The most important factor contributing to degradation is availability of oxygen during storage. With careful selection of storage condition to protect products from such facts as air by storing in an inert atmosphere or under vacuum, it is possible to retain initial colour levels during storage.
Antioxidant application: The main cause of damage to lycopene during food processing and storage is oxidation. Careful application of suitable antioxidants (Ethoxyquin, ascorbic acid, sodium acid pyrophosphate) at appropriate levels could have beneficial results. Low storage temperature, low light, low water activity, low moisture in storage will also have a limiting effect on the oxidation of lycopene.
Lycopene has a dual influence on production and quality as natural colour and nutrients for the food and pharma industry. Lycopene may be considered as “vitamin of the 21st century” because of its significant physiological effect on the human diet.
The fruit development processes leading up to fruit maturation may also have an effect on fruit components such as lycopene. Lycopene content in tomato fruit may be enhanced by improved techniques in fertilization, harvest time and variety selection. This focus may lead to higher quality tomato produced in green houses during winter.
The bio-availability of lycopene in foods is influenced not only by its isomeric forms, but also by the food matrix, the presence of sufficient bulk lipids for micellization of released lycopene and the presence of interfering factors in the lumen such as pectin and other dietary fibres. The degradation of lycopene is very important in tomato based food industry. Processing technology should be optimized to prevent lycopene oxidation and isomerisation.
Industrial production of lycopene from tomatoes is in high demand by pharmaceutical companies and for functional food development. At present, large quantity of skin and outer pericarp tissues are normally discarded as tomato processing waste in the peeling procedure of the tomato processing. Some new technologies such as membrane separation technology, supercritical fluid carbon dioxide technology and solvent extraction technology are being applied to scale up the lycopene production. High quality lycopene products that meet food safety regulation will offer potential benefits to the food industry. A successful commercialization of high value lycopene production may improve the competitiveness of tomato based products and lycopene products in the global market.
Numerous studies have shown that eating foods high in lycopene are beneficial in avoiding heart disease and several types of cancer such as lung, prostate, cervical, digestive tract and breast. Recent studies are looking at the effects of lycopene on such conditions as macular degenerative disease and serum lipid oxidation.
Those who support the above findings urge people to include lycopene in their diet for general good health. Good sources of lycopene are pink grapefruit, guava, watermelon, and rose hips, but the most common and perhaps the most potential is tomato.
Fresh tomatoes are an excellent source of lycopene, but cooked tomato products such as tomato and pizza sauce, tomato juice, tomato soup, and even ketchup, are more concentrated. For example, one fresh tomato contains 3.7 mg of lycopene, while one cup of tomato soup has 24.8 mg of lycopene. Because of the cis-form of lycopene in this cooked type of tomato product, the body can more easily absorb this lycopene.
Not everyone has accepted the benefits of lycopene. The world health regulatory agencies have not yet endorsed lycopene as a nutrient, but because of the promising results of early research, the health community is taking a serious look at the beneficial effects of lycopene in the diet. Of course, most health professionals agree that a diet rich with fruits and vegetables is part of a healthy lifestyle.
U.S. Pat. No. 5,837,311, Zelkha et al. (1998) describe a process for the extraction of lycopene from tomato pulp by extraction with solvents having delta H and delta P values. The oleoresin was obtained through this process having 2-10% lycopene content. However, the authors have not reported the purification step.
U.S. Pat. No. 5,897,866, Bombardelli et al. (1999) describe a process for the extraction of lycopene from tomato by using n-hexane and a chlorinated solvent. The process involved consists of extraction followed by column chromatographic separation which is tedious and industrial feasibility is questionable. There is no mention about the purity of isolated lycopene crystals.
Ausich et al. U.S. Pat. No. 5,858,700 (1999) reported the preparation of lycopene crystals from tomato and tomato products employing saponification with alkali and propylene glycol. The 90% lycopene crystals were obtained through this process with no mention of the isomeric form.
Kawaragi et al. U.S. Pat. No. 5,871,574 (1999) teaches the enzyme mediated extraction and purification of lycopene by using organic solvent. The product obtained through this process reported more than 10% lycopene content.
Konya et al. U.S. Pat. No. 6,331,652 (2001) reported a process for the preparation of lycopene. The process essentially is a chemical method involving multi stage reaction followed by column chromatographic separation and purification.
Estrella Decastro Antonio et al. EP 1201762 (2002) reported a process for the preparation of lycopene from fungal sources like blakeslea, choanephora or phycomyces. Ethyl acetate and ethyl alcohol and isopropyl alcohol were used for the extraction and purification, obtaining 94% purity of lycopene crystals though this process.
Giori et al. WO 03/079816 (2003) have described a process for the extraction and purification of lycopene from fresh tomato. The fresh tomatoes are crushed; water removed by vacuum distillation to obtain tomato concentrate. This concentrate is subjected to the extraction with water saturated ethyl acetate twice. This extract is washed with water and concentrated to obtain tomato oleoresin with 6% lycopene content. The concentrate is further washed with water, ethyl acetate and also by washing with ethanol (45 degrees C.) ageing and washing with ethyl acetate, to obtain crystalline lycopene with 95% purity.
Ho et al. WO 036125 (2006), have described a bio-process starting from tomato paste. (1) fermentation to remove sugars (2) enzyme mixtures to release the pigments from chloroplast and phytic acid, washed to remove heavy metals followed by sterilization and extraction with propane/butane gas yielding tomato extract containing 13% lycopene content.